Apache Mina通信框架架構與應用

Apache Mina Server 是一個網絡通信應用框架，也就是說，它主要是對基于 TCP/ip、UDP/IP協議棧的通信框架（當然，也可以提供 java 對象的序列化服務、虛擬機管道通信服務等），Mina 可以幫助我們快速開發高性能、高擴展性的網絡通信應用，Mina 提供了事件驅動、異步（Mina 的異步 IO 默認使用的是 JAVA NIO 作為底層支持）操作的編程模型。從官網文檔“MINA based application Architecture”中可以看到Mina作為一個通信層框架，在實際應用所處的位置，如圖所示： apparch_small Mina位于用戶應用程序和底層Java網絡API（和in-VM通信）之間，我們開發基于Mina的網絡應用程序，就無需關心復雜的通信細節。

應用整體架構

再看一下，Mina提供的基本組件，如圖所示： mina_app_arch 也就是說，無論是客戶端還是服務端，使用Mina框架實現通信的邏輯分層在概念上統一的，即包含如下三層：

I/O Service – Performs actual I/OI/O Filter Chain – Filters/Transforms bytes into desired Data Structures and vice-versaI/O Handler – Here resides the actual business logic

想要開發基于MIna的應用程序，你只需要做如下事情：

Create an I/O service – Choose from already available Services (*Acceptor) or create your ownCreate a Filter Chain – Choose from already existing Filters or create a custom Filter for transforming request/responseCreate an I/O Handler – Write business logic, on handling different messages

下面看一下使用Mina的應用程序，在服務器端和客戶端的架構細節：

服務器端架構服務器端監聽指定端口上到來的請求，對這些請求經過處理后，回復響應。它也會創建并處理一個鏈接過來的客戶會話對象（session）。服務器端架構如圖所示： Server_arch 對服務器端的說明，引用官網文檔，如下所示：

IOAcceptor listens on the network for incoming connections/packetsFor a new connection, a new session is created and all subsequent request from IP Address/Port combination are handled in that SessionAll packets received for a Session, traverses the Filter Chain as specified in the diagram. Filters can be used to modify the content of packets (like converting to Objects, adding/removing information etc). For converting to/from raw bytes to High Level Objects, PacketEncoder/Decoder are particularly usefulFinally the packet or converted object lands in IOHandler. IOHandlers can be used to fulfill business needs.

客戶端架構客戶端主要做了如下工作：

連接到服務器端向服務器發送消息等待服務器端響應，并處理響應

客戶端架構，如圖所示： clientdiagram 對客戶端架構的說明，引用官網文檔內容，如下所示：

Client first creates an IOConnector (MINA Construct for connecting to Socket), initiates a bind with ServerUpon Connection creation, a Session is created and is associated with ConnectionApplication/Client writes to the Session, resulting in data being sent to Server, after traversing the Filter ChainAll the responses/messages received from Server are traverses the Filter Chain and lands at IOHandler, for PRocessing

應用實例開發

下面根據上面給出的架構設計描述，看一下Mina（版本2.0.7）自帶的例子，如何實現一個簡單的C/S通信的程序，非常容易。服務端首先，服務器端需要使用的組件有IoAdaptor、IoHandler、IoFilter，其中IoFilter可選.我們基于Mina自帶的例子進行了簡單地修改，實現服務端IoHandler的代碼如下所示：

`01`	`package` `org.shirdrn.mina.server;`

02

`03`	`import` `org.apache.mina.core.service.IoHandlerAdapter;`

`04`	`import` `org.apache.mina.core.session.IdleStatus;`

`05`	`import` `org.apache.mina.core.session.IoSession;`

`06`	`import` `org.slf4j.Logger;`

`07`	`import` `org.slf4j.LoggerFactory;`

08

`09`	`public` `class` `TinyServerProtocolHandler` `extends` `IoHandlerAdapter {`

`10`	`private` `final` `static` `Logger LOGGER = LoggerFactory.getLogger(TinyServerProtocolHandler.class);`

11

`12`	`@Override`

`13`	`public` `void` `sessionCreated(IoSession session) {`

`14`	`session.getConfig().setIdleTime(IdleStatus.BOTH_IDLE,` `10);`

15 }

16

`17`	`@Override`

`18`	`public` `void` `sessionClosed(IoSession session)` `throws` `Exception {`

`19`	`LOGGER.info("CLOSED");`

20 }

21

`22`	`@Override`

`23`	`public` `void` `sessionOpened(IoSession session)` `throws` `Exception {`

`24`	`LOGGER.info("OPENED");`

25 }

26

`27`	`@Override`

`28`	`public` `void` `sessionIdle(IoSession session, IdleStatus status) {`

`29`	`LOGGER.info("* IDLE #"` `+ session.getIdleCount(IdleStatus.BOTH_IDLE) +` `" *");`

30 }

31

`32`	`@Override`

`33`	`public` `void` `exceptionCaught(IoSession session, Throwable cause) {`

`34`	`session.close(true);`

35 }

36

`37`	`@Override`

`38`	`public` `void` `messageReceived(IoSession session, Object message)`

`39`	`throws` `Exception {`

`40`	`LOGGER.info(` `"Received : "` `+ message );`

`41`	`if(!session.isConnected()) {`

`42`	`session.close(true);`

43 }

44 }

45 }

這個版本中，IoHandlerAdapter實現了IoHandler接口，里面封裝了一組用于事件處理的空方法，其中包含服務端和客戶端的事件。在實際應用中，客戶端可以選擇客戶端具有的事件，服務器端選擇服務器端具有的事件，然后分別對這兩類事件進行處理（有重疊的事件，如連接事件、關閉事件、異常事件等）。客戶端的IoHandler的具體實現也是類似的，不過多累述。下面看啟動服務器的主方法類，代碼如下所示：

`01`	`package` `org.shirdrn.mina.server;`

02

`03`	`import` `java.net.InetSocketAddress;`

04

`05`	`import` `org.apache.mina.filter.codec.ProtocolCodecFilter;`

`06`	`import` `org.apache.mina.filter.codec.textline.TextLineCodecFactory;`

`07`	`import` `org.apache.mina.transport.socket.SocketAcceptor;`

`08`	`import` `org.apache.mina.transport.socket.nio.NioSocketAcceptor;`

`09`	`import` `org.slf4j.Logger;`

`10`	`import` `org.slf4j.LoggerFactory;`

11

`12`	`public` `class` `TinyMinaServer {`

13

`14`	`private` `final` `static` `Logger LOG = LoggerFactory.getLogger(TinyMinaServer.class);`

`15`	`/** Choose your favorite port number. */`

`16`	`private` `static` `final` `int` `PORT =` `8080;`

17

`18`	`public` `static` `void` `main(String[] args)` `throws` `Exception {`

`19`	`SocketAcceptor acceptor =` `new` `NioSocketAcceptor();`

`20`	`acceptor.setReuseAddress(true);`

`21`	`acceptor.getFilterChain().addLast("codec",` `new` `ProtocolCodecFilter(newTextLineCodecFactory()));`

22

23 // Bind

`24`	`acceptor.setHandler(new` `TinyServerProtocolHandler());`

`25`	`acceptor.bind(new` `InetSocketAddress(PORT));`

`26`	`LOG.info("Listening on port "` `+ PORT);`

27

`28`	`LOG.info("Server started!");`

29

`30`	`for` `(;;) {`

`31`	`LOG.info("R: "` `+ acceptor.getStatistics().getReadBytesThroughput() +` `", W: "` `+ acceptor.getStatistics().getWrittenBytesThroughput());`

`32`	`Thread.sleep(3000);`

33 }

34 }

35

36 }

客戶端實現客戶端IoHandler的代碼如下所示：

`01`	`package` `org.shirdrn.mina.client;`

02

`03`	`import` `org.apache.mina.core.service.IoHandlerAdapter;`

`04`	`import` `org.apache.mina.core.session.IdleStatus;`

`05`	`import` `org.apache.mina.core.session.IoSession;`

`06`	`import` `org.slf4j.Logger;`

`07`	`import` `org.slf4j.LoggerFactory;`

08

`09`	`public` `class` `TinyClientProtocolHandler` `extends` `IoHandlerAdapter {`

10

`11`	`private` `final` `static` `Logger LOGGER = LoggerFactory`

`12`	`.getLogger(TinyClientProtocolHandler.class);`

13

`14`	`@Override`

`15`	`public` `void` `sessionCreated(IoSession session) {`

`16`	`LOGGER.info("CLIENT::CREATED");`

17 }

18

`19`	`@Override`

`20`	`public` `void` `sessionClosed(IoSession session)` `throws` `Exception {`

`21`	`LOGGER.info("CLIENT::CLOSED");`

22 }

23

`24`	`@Override`

`25`	`public` `void` `sessionOpened(IoSession session)` `throws` `Exception {`

`26`	`LOGGER.info("CLIENT::OPENED");`

27 }

28

`29`	`@Override`

`30`	`public` `void` `sessionIdle(IoSession session, IdleStatus status) {`

`31`	`LOGGER.info("CLIENT::*** IDLE #"`

`32`	`+ session.getIdleCount(IdleStatus.BOTH_IDLE) +` `" ***");`

33 }

34

`35`	`@Override`

`36`	`public` `void` `exceptionCaught(IoSession session, Throwable cause) {`

`37`	`LOGGER.info("CLIENT::EXCEPTIONCAUGHT");`

`38`	`cause.printStackTrace();`

39 }

40

`41`	`public` `void` `messageSent(IoSession session, Object message)` `throws` `Exception {`

`42`	`LOGGER.info("CLIENT::MESSAGESENT: "` `+ message);`

43 }

44 }

下面看啟動客戶端的主方法類，代碼如下所示：

`01`	`package` `org.shirdrn.mina.client;`

02

`03`	`import` `java.net.InetSocketAddress;`

04

`05`	`import` `org.apache.mina.core.future.ConnectFuture;`

`06`	`import` `org.apache.mina.filter.codec.ProtocolCodecFilter;`

`07`	`import` `org.apache.mina.filter.codec.textline.TextLineCodecFactory;`

`08`	`import` `org.apache.mina.transport.socket.SocketConnector;`

`09`	`import` `org.apache.mina.transport.socket.nio.NioSocketConnector;`

`10`	`import` `org.slf4j.Logger;`

`11`	`import` `org.slf4j.LoggerFactory;`

12

`13`	`public` `class` `TinyMinaClient {`

14

`15`	`private` `final` `static` `Logger LOG = LoggerFactory.getLogger(TinyMinaClient.class);`

`16`	`/** Choose your favorite port number. */`

`17`	`private` `static` `final` `int` `PORT =` `8080;`

18

`19`	`public` `static` `void` `main(String[] args)` `throws` `Exception {`

`20`	`SocketConnector connector =` `new` `NioSocketConnector();`

21

`22`	`// Connect`

`23`	`connector.getFilterChain().addLast("codec",` `new` `ProtocolCodecFilter(newTextLineCodecFactory()));`

`24`	`connector.setHandler(new` `TinyClientProtocolHandler());`

25

`26`	`for` `(int` `i =` `0; i <` `10; i++) {`

`27`	`ConnectFuture future = connector.connect(new` `InetSocketAddress(PORT));`

`28`	`LOG.info("Connect to port "` `+ PORT);`

`29`	`future.awaitUninterruptibly();`

`30`	`future.getSession().write(String.valueOf(i));`

`31`	`Thread.sleep(1500);`

32 }

33

34 }

35 }

我們只是發送了十個數字，每發一次間隔1500ms。測試上述服務器端與客戶端交互，首先啟動服務器端，監聽8080端口。接著啟動客戶端，連接到服務器端8080端口，然后發送消息，服務器端接收到消息后，直接將到客戶端的連接關閉掉。